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From: Ask Kaereby <ask@...>
Date: Thu Feb 14, 2002 5:32pm
Subject: [OT] 24/96 - it's all in the filter!

The reason why 96 kHz sounds better than 44.1 has to do with the
anti-alias filter. With 44.1 any frequency above 22.05kHz will produce
alias artifacts (as described by Nyquist) so they must be removed by
means of a filter. If you want 20-20kHz response, you must construct a
filter that (ideally) will pass 20kHz at full level and dampen
22.05kHz below the threshold of hearing (-96dB should do for 16bit).
Thats a filter slope of ~ 1000dB/octave!!!  AFAIK all constructed
filters of this type compromise either frequency response or
anti-aliasing and possibly also phase integrity. For comparison, with
96kHz a filter starting at 20kHz only needs a slope of ~ 100dB/oct. It
is possible to construct such a filter with only neglectible impact,
if any, on the audio quality.


Ask Kaereby

www.audioengineer.com/ask